1. Field of the Invention
The present invention relates to an apparatus for continuous polymerization for producing a vinyl chloride homopolymer or a vinyl chloride-based copolymer (hereinafter generically referred to as "vinyl chloride-based polymer") by suspension polymerization of vinyl chloride or a vinyl chloride-based monomeric mixture (hereinafter generically referred to as "vinyl chloride-based monomeric material").
2. Description of the Prior Art
Heretofore, suspension polymerization of a vinyl chloride-based monomeric material has been carried out by a batch polymerization process in which water, the vinyl chloride-based monomeric material, a polymerization initiator and a dispersant, together with other various additives as required, are placed into a polymerization vessel equipped with a jacket and a reflux condenser, and cooling water is passed through the jacket and reflux condenser to remove the heat of polymerization, thereby controlling the temperature of the reaction system to a predetermined temperature.
In order to enhance productivity of the polymerization vessel in practicing the conventional process, it is necessary to increase the amount of the vinyl chloride-based monomeric material placed into the polymerization vessel or to shorten the polymerization time. In any of the cases, the heat of reaction per unit time is increased. Consequently, cooling capability of the polymerization apparatus used would come to be an issue. Conventionally, various methods have been adopted for coping with this problem, for example, a method by lowering the temperature of the cooling water passed through the jacket to achieve more powerful cooling, or a method by increasing the quantity of heat removed by the reflux condenser.
However, the former method is expensive and therefore unadvantageous economically, and the latter method has the drawback that carry-over arises from foaming of the polymerization reaction mixture, leading to polymer scale formation, or the number of fish-eyes in the resulting polymer product is increased.
On the other hand, continuous polymerization process is advantageous from a productivity point of view. In the case of vinyl chloride polymers, however, no continuous polymerization process has been successfully put to practical use, because of difficulties as to product quality (especially, fish-eye), polymer scale deposition and the like.